Abby awakens to banging on the door, sees a truck crashed, and finds her baby sister crying out for breakfast. She soon discovers why Dad hasn't fed her.

Astronomers predicted that Earth would pass through a comet's tail, turning the moon purple. But nobody predicted that bacteria from the comet would attack the hormones responsible for puberty. Adults died within hours.

Abby struggles to care for her siblings while quarantined scientists race to find a cure. The time bomb of puberty ticks louder the older Abby gets.